As lead-based materials continue to be undesirable for ammunition and other applications due to their intrinsic toxicity, realistic economic substitutes will become more needed. Metallic-based solutions are preferable due to potential densities and performance requirements; toughness and/or frangibility. Traditional all-metal bullets are designed to either penetrate armors or maximize energy transfer on target via hollow-point and/or expanding technologies.
Copper offers the next-best material of choice based on its physical characteristics; density, toughness, and formability. Unfortunately, despite its relative abundance, the cost of copper, is up to five times the cost of lead and therefore limits its acceptance. Iron is notably less expensive but also less dense. Iron alone is not a practical solution due to its tendency to create sparks exiting the muzzle and on impact with steel targets. Iron alone can also potentially be classified as armor-piercing.
These two common metals can be combined as separate powders and formed using typical powder metallurgy methods but the degree of mixing, and therefore performance, is notably limited due to practical particle sizes. Mechanical alloying is also a viable approach but is less attractive due to the relative cost of this high energy, batch process.